The incidence of cytomegalovirus retinitis has decreased in human immunodeficiency virus (HIV)-infected patients concomitant with the widespread use of highly actively antiretroviral therapy (HAART). However despite this decrease, there are HIV infected patients who are still at risk for CMV retinitis because they do not/cannot follow the prescribed therapeutic regimen of anti-HIV drugs. Therefore, an increased understanding of the mechanisms underlying the pathogenesis of CMV has the potential for translation into preventative or ameliorative treatments in patients who are at still at risk for developing CMV retinitis. In this application, a combination of in vitro and in vivo studies using mice, mouse tissues, and cultured cells are proposed to decipher the mechanism of several features of murine cytomegalovirus (MCMV) retinitis including the process of sequential infection from the outer retina (following inoculation of virus via the supraciliary route which allows the virus to gain access to the subretinal space) to the inner retina and the observation from both mouse and from human studies that cytomegalovirus infected cells usually do not undergo apoptosis. The studies proposed in this application will take advantage of recent advances in understanding apoptotic pathways and in how cytomegalovirus may interact with the host to induce retinal damage. The first specific aim will determine how infection of RPE cells induces apoptosis in the overlying retina. This aim will test the hypothesis that production of iNOS and NO by infected RPE cells begins the cascade of retinal infection and damage during MCMV retinitis. This aim will also allow us to determine the contribution of TNF-1 during initial infection of the RPE. The second Specific Aim will determine to what extent TNF-1 and NO cause apoptosis of uninfected retinal cells via caspase-dependent and caspase-independent pathways, respectively. This aim will test the hypothesis that caspase-dependent as well as caspase-independent apoptosis contributes to retinal pathology during MCMV retinitis. The third Specific Aim will determine why MCMV infected retinal cells do not undergo apoptosis. This aim will test the hypothesis that MCMV immediate early protein 3 (IE-3) plays an important role in protecting infected cells from apoptosis by upregulating the cellular FLICE-inhibitory protein (c-FLIP). The results of these studies will provide new information about the mechanisms of MCMV infection of the retina which may be applicable to new therapeutic approaches to prevent cytomegalovirus infection of the retina or to reduce retinal damage in human patients. PUBLIC HEALTH RELEVANCE: The incidence of cytomegalovirus retinitis has decreased in human immunodeficiency virus (HIV)-infected patients concomitant with the widespread use of highly actively antiretroviral therapy (HAART). Despite this decrease however, there are HIV infected patients who are still at risk for cytomegalovirus retinitis because they do not/cannot follow the prescribed therapeutic regimen of anti-HIV drugs or their virus becomes drug resistant. Increased understanding of the mechanisms underlying the pathogenesis of cytomegalovirus infections has the potential for translation into preventative or ameliorative treatments in patients who are at still at risk for development of CMV retinitis. Results of the proposed studies will provide new information about the mechanisms of cytomegalovirus infection of the retina which may be applicable to new therapeutic approaches to prevent retinal infection and/or to reduce retinal damage.